Typewriter platen releasing mechanism having an elastically deformable gear disc

ABSTRACT

A platen releasing mechanism in a typewriter, having a single spring disc incorporated in a clutching mechanism between a platen and a platen gear. The disc has gear serrations therearound and is adapted for engagement with associated gear serrations of the platen gear. The spring disc may be caused to be elastically deformed into a dished form, away from the platen gear, for disconnecting the platen from the platen gear by means of a push button disposed in a recess of a platen knob through an interlocking member. This releases the engagement of the platen with the platen gear for free manual rotation of the former, irrespective of the engagement between the platen gear and a line changing mechanism of the typewriter. This allows relocating at a printing position a previously typewritten line of characters, which may require the correction or letter or a addition of a letter or a character.

United States Patent 1 1 Terashima 1 June 17, 1975 [22] Filed: Nov. 28,1973 [21] Appl. No; 419,723

[30] Foreign Application Priority Data Apr. 2, 1973 Japan 48-38727[U][52] US. Cl. 197/123 [51] Int. Cl B4lj 19/80 [58] Field of Search197/114 R, 114 A, 114 B,

[56] References Cited 7 UNITED STATES PATENTS 11/1900 Wallace 197/1237/1910 Uhlig.... 197/123 1,749,835 3/1930 Myers r 197/123 FOREIGNPATENTS OR APPLICATIONS I.l3l,706 6/1962 Germany l97/l23 PrimaryExaminer-Ernest T. Wright, Jr. Attorney. Agenl, ur FirmHaseltine, Lake &Waters [57) ABSTRACT A platen releasing mechanism in a typewriter,having a single spring disc incorporated in a clutching mechanismbetween a platen and a platen gear. The disc has gear serrationstherearound and is adapted for engagement with associated gearserrations of the platen gear. The spring disc may be caused to beelastically deformed into a dished form, away from the platen gear, fordisconnecting the platen from the platen gear by means of a push buttondisposed in a recess of a platen knob through an interlocking member.This releases the engagement of the platen with the platen gear for freemanual rotation of the former, irrespective of the engagement betweenthe platen gear and a line changing mechanism of the typewriter. Thisallows relocating at a printing position a previously typewritten lineof characters, which may require the correction or letter or a additionof a letter or a character.

6 Claims, 4 Drawing Figures TYPEWRITER PLATEN RELEASING MECHANISM HAVINGAN ELASTICALLY DEFORMABLE GEAR DISC BACKGROUND OF THE INVENTION Thepresent invention relates in general to a typewriter, and particularlyto a platen releasing mechanism of the typewriter. More particularly,this invention is concerned with a mechanism incorporated within theplaten construction for releasing the engagement of the platen with aline changing mechanism, which is designed to release the engagement ofthe platen to enable the latter to be manually turned free from a presetrotating advancing motion of the platen, for the correction or additionof a previously typewritten letter or a character.

In a known typewriter design, there is provided a device designed forreleasing the platen from engagement with the line changing mechanismfor manual angular rotation of the platen, free from a preset linechanging or angular advancing motion by the line changing mechanism,thereby to enable the platen to be rotated by a desired angularadvancing motion so as to accurately relocate the position of a line tobe corrected or added with a letter or a charcter therein which waspreviously erroneously typewritten.

More specifically, a platen or a platen shaft is provided with aconnecting member which is designed to be axially slidable with respectto the platen or platen shaft by means of a slot or key constructionincorporated therein, and which connecting member is further providedwith gear serrations on the inner circumference thereof so that theconnecting member may be engaged with gear serrations of the same toothpitch, formed on the outer circumference of a piaten gear, which isintermittently driven by the line changing mechanism, for a stepwiserotating motion in accordance with a preset degree of rotation or, inother words, the desired line interval.

Normally the platen is engaged with the line changing mechanism of thetypewriter, and is intermittently rotated by the line changing mechanismthrough the abovementioned connecting member. When a button or the like,provided in a platen knob, is pushed or pulled so as to cause theconnecting member to slide axially with respect to the platen, thereoccurs a disengagement between the platen gear and the connecting memberincorporated within the platen, whereby the platen is allowed to berotated manually free from the line changing mechanism.

In the case of the typewriter construction wherein the platen gear isdirectly installed on the platen, the platen releasing mechanism is ofsuch construction that the connecting member, that engages the gearserrations provided on the platen gear as described above, is providedin an axially slidable manner with respect to the platen and the like bymeans ofa key and the like. Consequently, there might inevitably occur arelative play between the mutually engaging platen and the connectingmember due to wear in the keyway or the like, thus resulting in alongitudinal deviation or staggering of a typewritten line of characterswhich should be properly aligned with a straight line. For preventingsuch an occurrence it is essential to finish the key or the keyway byhigh-precision machining, which results in high production costs.

This invention is particularly directed to cope with such drawbacksaccompanying the conventional platen releasing mechanisms as describedabove.

SUMMARY OF THE INVENTION It is therefore a primary object of thisinvention to provide a novel and useful platen releasing mechanismhaving advantageous features over the conventional mechanisms such asbeing much simpler yet more reliable, and having a durable constructionwith the resultant relatively low manufacturing costs.

It is another object of this invention to provide a unique and usefulplaten releasing mechanism which does not require any keyway or the likein the construction thereof, that would necessitate high precisionmachining, and which is entirely free from play between the platen andthe platen gear due to wear thereof dur ing use, thus effectivelypreventing deviation or staggering in the line of typewrittencharacters.

The foregoing and other objects, characteristics and advantages of theinvention will be more fully understood from the following detaileddescription of a preferred embodiment thereof, when read with referenceto the accompanying drawing, in which like parts are designated by likereference numerals.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a front view, partly in longitudinal section, showing apreferred, exemplary embodiment of the platen releasing mechanismaccording to this invention;

FIG. 2 is a perspective view, partly cut away, showing a platen arborused in the mechanism of this invention;

FIG. 3 is a front veiw showing an example of a resilient disc, having agear serration therearound', and

FIG. 4 is a front view of a modified example of the resilient disc,having a ring member fixed therearound.

DETAILED DESCRIPTION Referring now to FIG. 1, there is shown aconventional platen l of a typewriter, in fragmentary longitudinalsection, and in the interior of one end of the platen l a boss 2 havinga cylindrical sleeve 2a is press fitted.

In the interior of the sleeve 20 is inserted a sleeve-like extension 30of a platen gear 3 to be driven by a conventional line changingmechanism of the typewriter in such a manner that it may rotate in andalong the inner circumference of the sleeve 2a. A projection 2b will bedescribed somewhat later.

On the outer circumference of the outer end of the platen gear 3, thereis provided a ratchet wheel 3a for driven engagement with a driving pawl(not shown) of the line changing mechanism, while there is formed anopening (preferably, a frustoconical opening) in the free or inner endof the sleevelike extension 3c, as shown in FIG. 1. Inner gearserrations 3b are formed on the inner frusto-conical surface of theopening.

On the other hand, in the central portion of the boss 2, a platen arbor5 is threadedly fitted at the right end thereof as viewed in FIG. 1, theplaten arbor 5 having a knob 4 at the opposite or left end thereof.Projections 4a will be described further down. More specifically, theplaten arbor 5 comprises an extension 6 ofa smaller diameter havingscrew-threads 6a thereon for threaded engagement with the boss 2, and abarrel portion 7 of a larger diameter extending outwardly from theplaten 1 when installed, and there is formed a shoulder 7a between theextension 6 and the barrel portion 7.

The barrel portion 7 is provided therein with a bore 7b extending in theaxial direction thereof and opening outwardly therefrom, and is furtherprovided with a plurality of, for instance, two radial slots 7coriginating from the shoulder 70 and extending in the axial direction tojoin with the abovementioned bore 719. The screw threads 60 areleft-hand threads so that they are prevented from being loosened due tothe rotation of the platen 1 during typographical operations.

On the extension 6 of the platen arbor 5, there is disposed a resilientdisc 8, as shown in FIG. 3, which is made of elastic metal, for example,and has outer gear serrations 8a on the outer circumference thereof formeshing engagement with the inner gear serrations 3b on thefrustoconical surface of the platen gear 3, the resilient disc 8 beingrigidly clamped between the shoulder 7a and the earlienmentioned annularprojection 2b, formed on the central portion of the boss 2, so that theresilient disc 8 may not be loosened relative to the boss 2 and hencethe platen 1 during the operation.

There is disposed a cylindrical sleeve member 9 on the outercircumference of the barrel portion 7 of the platen arbor 5, the innerend portion thereof facing the platen l and having an enlarged diameterwhich is in contact with the outer marginal portion of the resilientdisc 8. At the outer end (opposite to the platen side) of theabovementioned cylindrical sleeve member 9, there are provided, forinstance, two arms 9a projecting radially inwardly through therespective slots 70 into the axial bore 7b in the barrel portion 7, sothat the member 9 can slide relative to the arbor only in the axialdirection thereof.

In the axial bore 7b of the platen arbor 5, there is inserted a coremember 11 under the bias of a resilient member such as a compressioncoil spring 10. The inner end of the member 11 abuts the abovementionedarms 90, while the outer end of the member 11 is provided with a pushbutton 12. The latter is set in position in a recess of the platen knob4 in such a manner that a flanged portion 12a formed on the outercircumference of the push button 12 abuttingly engages the earliermentioned, radially inwardly extending projections 4a on the platen knob4, whereby the core member 11 is prevented from axially outwardly movingbeyond the position shown in FIG. 1 under the bias of the spring 10.Parts 18, 18a, 18b will be described later in connec tion with FIG. 4.

The operation of the platen releasing mechanism will now be described.In the condition shown wherein the core member [1 is being urged in theoutward direction or to the left as viewed in FIG. 1 under the bias ofthe spring 10, and wherein the flanged portion 120 of the push button 12is kept in abutting engagement with the projections 4a of the platenknob 4, the resilient disc 8 is kept free from the pushing force of thecylindrical sleeve member 9. Therefore, meshing engagement isestablished between the inner gear serrations 3b on the frusto-conicalsurface of the platen gear 3 and the outer gear serrations 8a on theresilient disc 8.

Consequently, the platen l and the platen gear 3 may now be caused towork as an integral unit through the resilient disc 8 and the boss 2,the platen 1 being thus driven in rotation by the line changingmechanism (not shown) of the typewriter in accordance with a presetextent of rotation or anguglar advancing motion in terms of a givenpitch of the ratchet wheel 3a on the platen gear 3.

In contrast, when the push button 12 is manually pushed against the biasof the spring 10 so as to move the core member 11 inwardly, thecylindrical sleeve member 9 is caused to travel axially inwardly alongthe platen arbor 5, toward the right as viewed in FIG. I, with the innerend (the rightmost part in FIG. 1) of the member 11 abutting the arms 9aof the member 9. By this travel of the member 9, the peripheral portionof the resilient disc 8 is caused to be deformed or warped elasticallyaway from the serrations 3b in the inward direction of the platen 1,thereby disengaging the serrations 8a from the serrations 3b and thuspermitting the platen l and the platen gear 3 to be disconnected fromeach other for free manual rotation.

As a consequence, when the platen knob 4 is manually turned in thisstate, although the platen gear 3 is still in engagement with the linechanging mechanism, of the platen 1 can be rotated manually, entirelyfree from the line changing mechanism, and can be realigned to meet anyangular position of a line of characters on the paper, which requirescorrection or addition of a letter or a character previouslytypewritten.

When the push button 12 is released, the core member 11 returns to theoriginal position thereof as shown in FIG. 1, thus the resilient disc 8assumes its original flat form again by its own resilience so that theengagement between the outer gear serrations 8a of the resilient disc 8and the inner gear serrations 3b of the platen gear 3 may be restored.Consequently, the platen gear 3 is connected to the platen 1 and thelatter is brought under the control of the line changing mechanism.

As an alternative example, the resilient disc 8 may be of a constructioncomprising a single resilient disc 18 and a ring member 18b secured tothe disc 18 and having outer gear serrations 18a as illustrated in FIG.4.

As described hereinbefore, according to the present invention, there isprovided a unique and useful platen releasing mechanism which featuresthe following advantages over conventional mechanisms. By virtue of theuse of the spring disc having resilience in the axial direction of theplaten, while having rigidity in the rotating direction of the platenover the entire circumference thereof, used for the engagement betweenthe platen and the platen gear, there is no need for the provision ofany key construction in the power transmitting portion between the twomembers as in conventional mechanisms, which would inevitably result inhigh production costs.

In addition, the platen releasing mechanism according to this inventionfeatures a simple yet reliable and durable construction, which in turnenables the production as well as the maintenance costs to be cutsubstantially.

What I claim is:

l. A releasing mechanism for a cylindrical platen of a typewriter, thetypewriter further including a line changing mechanism, the releasingmechanism comprising, in combination: a boss secured in the interior ofsaid platen at one end thereof; a platen gear rotatably and coaxiallyinserted in said boss and having means forming an opening with inner,first gear serrations at the axially inner end thereof, and a ratchetwheel on the outer circumference and at the axially 0pposite endthereof, for driven engagement with said line changing mechanism; aplaten arbor having the axially inner end rigidly secured to a centralportion of said boss. and the other end extended outwardly from saidplaten in the axial direction of said platen; a platen knob secured tothe outer end of said arbor; a resilient. disc-shaped member rigidlymounted on said arbor and having second gear serrations on the outercircumferencc thereof for meshing engagement with said first gearserrations; a sleeve member mounted on said arbor. slidable in the axialdirection of said arbor nonrotatable relative to said arbort andabutting a radially outer portion of said resilient member; andoperating means axially slidably mounted in said arbor. having one endthereof in contact with said sleeve member. and the other end thereofmanually pushable from out side; the manual pushing operation on saidoperating means causing said sleeve member to deform said resilientmember in a manner that said second gear serrations move out of meshingengagement with said first gear serrations, whereby driving connectionbetween said gear and said platen is broken.

2. The platen releasing mechanism as defined in claim 1, wherein saidarbor includes a smaller diameter extension and a larger-diameter barrelportion with a shoulder formed therebetween, and wherein said extensionis threadly secured to said boss, and said resilient member is rigidlyclamped between said boss and said shoulder.

3. The platen releasing mechanism as defined in claim 1, wherein saidopening having said first gear serrations is in the form ofafrusto-conical opening diverging toward an axially central part of saidplaten.

4. The platen releasing mechanism as defined in claim I, wherein saidarbor has an axial bore therein and said operating means includes a coremember re ceived in said bore. and further comprising a push buttondisposed in said knob. rigidly secured to the axially outer end of saidcore member.

5. The platen releasing mechanism as defined in claim 4. furthercomprising a spring disposed in said arbor and resiliently urging saidcore member in an axially outward direction, and further comprisingmeans for limiting the axial outward movement of said core member.

6. The platen releasing mechanism as defined in claim 4, wherein saidarbor has at least one axially extending radial slot joining said borein the arbor. said sleeve member has at least one arm passed radiallythrough said slot into said bore. and wherein said arm is in contactwith the axially inner end of said core

1. A releasing mechanism for a cylindrical platen of a typewriter, thetypewriter further including a line changing mechanism, the releasingmechanism comprising, in combination: a boss secured in the interior ofsaid platen at one end thereof; a platen gear rotatably and coaxiallyinserted in said boss and having means forming an opening with inner,first gear serrations at the axially inner end thereof, and a ratchetwheel on the outer circumference and at the axially opposite endthereof, for driven engagement with said line changing mechanism; aplaten arbor having the axially inner end rigidly secured to a centralportion of said boss, and the other end extended outwardly from saidplaten in the axial direction of said platen; a platen knob secured tothe outer end of said arbor; a resilient, disc-shaped member rigidlymounted on said arbor and having second gear serrations on the outercircumference thereof for meshing engagement with said first gearserrations; a sleeve member mounted on said arbor, slidable in the axialdirection of said arbor, non-rotatable relative to said arbor, andabutting a radially outer portion of said resilient member; andoperating means axially slidably mounted in said arbor, having one endthereof in contact with said sleeve member, and the other end thereofmanually pushable from outside; the manual pushing operation on saidoperating means causing said sleeve member to deform said resilientMember in a manner that said second gear serrations move out of meshingengagement with said first gear serrations, whereby driving connectionbetween said gear and said platen is broken.
 2. The platen releasingmechanism as defined in claim 1, wherein said arbor includes asmaller-diameter extension and a larger-diameter barrel portion with ashoulder formed therebetween, and wherein said extension is threadlysecured to said boss, and said resilient member is rigidly clampedbetween said boss and said shoulder.
 3. The platen releasing mechanismas defined in claim 1, wherein said opening having said first gearserrations is in the form of a frusto-conical opening diverging towardan axially central part of said platen.
 4. The platen releasingmechanism as defined in claim 1, wherein said arbor has an axial boretherein and said operating means includes a core member received in saidbore, and further comprising a push button disposed in said knob,rigidly secured to the axially outer end of said core member.
 5. Theplaten releasing mechanism as defined in claim 4, further comprising aspring disposed in said arbor and resiliently urging said core member inan axially outward direction, and further comprising means for limitingthe axial outward movement of said core member.
 6. The platen releasingmechanism as defined in claim 4, wherein said arbor has at least oneaxially extending radial slot joining said bore in the arbor, saidsleeve member has at least one arm passed radially through said slotinto said bore, and wherein said arm is in contact with the axiallyinner end of said core member.